Honestly? Probably never or at best not any time soon. This isn't currently on anyone's radar.
As waffles mentioned in his comment, the DB schemas are different between A51 and the Q&A sites which further complicates matters. Plus, unlike with active Q&A, there's just not much benefit from having A51 in the data explorer. I'm willing to bet that just about nobody would use it.
That said, if you want to grab some A51 data for analysis, drop me an email and I'll see what I can do.